Let's say I have a crafted item that can be used by evil-aligned charcters only, and if a good-aligned character wields it they have a chance of becoming evil-aligned. How would I make this is a DC? or is it %d?

Personally, I'd make it a Will save. Depending on how difficult you want to make it, I would suggest a DC of 17 or greater. To make it really hard, use a DC of 25+. Private notes to the PC to suggest the slow personality change are good, accomanied with further will checks. Remember, the item is forcing it's will on the PC, and total subversion could take a long time. Once the subversion starts, make the PC make Will checks to to GOOD acts, until you feel that the PC has been completly corrupted. Great role playing ops here.

D&D rules are hard to keep up with lately Nanobyte. Going back to it's origin say you picked up a low level Balrog sword. It was an Evil +1 flamming sword. Magical swords always got a dice roll to see how powerful it really was. So if a low level character picked it up often times they couldn't put it down without a dispell majic.
Then sometimes the sword wouldn't pocess the person until battle. Like a berserk spell gone bad on the party.

These are most likely outdated rules by now but that was part of the original 3 book style. Very exciting and from hence it grew.

So I would say yes to the evil draw on the sword. It should be dispelled off if you have to. I'll go away now ;) </p> D. W.